Patent GB-1080598-A (GB)
Title: Apparatus for use in ultrasonic rail testing
Inventor: JOY IVAN L
IPC: G01N29/06
Filed: 1963-12-12
Abstract: 1,080,598. Ultrasonic testing; cathode-ray tube circuits. CHEMETRON CORPORATION. Dec. 12, 1963, No. 49202/63. Headings H4D and H4T. Apparatus for the ultrasonic testing of rail utilizes a memory type cathode-ray display tube the beam of which is intensity modulated by received pulse echo signals and scanned in rectangular co-ordinate directions at the rate of transmission of test pulses and at a much lower rate the display being erased at the end of each deflection at the lower rate. The persistence and continuity of the display so produced is stated to result in improved accuracy and reliability in the evaluation of the presentation. In one embodiment ultrasonic echo pulses from a transducer 22 (Fig. 1) fed by an ultrasonic generator 21 controlled by rate generator 20 and water coupled to a rail R along which it is progressed are fed to the beam intensity control electrode 11 of the memory tube T via a gate 23 which removes the transmitted pulses, the beam being deflected in one co-ordinate direction at the rate of generator 20 (pulses 20<SP>a</SP>) by scan generator 24 feeding deflection means 13 and in the other co-ordinate direction by a scan generator 26 (waveform 26S) operating at a much lower rate than generator 24. At the end of each sweep of generator 26 a pulse generator 29 supplies an erase pulse to the storage mesh 12 and simultaneously operates via a voltage dropping network 18 to cause havy conduction in valve 17 and thereby reduce the 9.5 kv. supply to the screen 10. To avoid loss of information during the erasure interval of the tube display a gate 30 responsive to echoes during this interval supplies an indicator 31 which may be a cathode-ray tube, a chronograph tape, a bell, a light or a similar device. To ensure that erase intervals do not occur in the vicinity of rail joint and bolt-hole regions the initiation of scanning may be controlled by a device (e.g. a coil) responsive to rail joints. By employing two sets of ultrasonic devices progressed along each rail simultaneously and supplying echo signals from each to the beam control electrode in alternating sequence representations of both rails may be displayed simultaneously in side-by-side relationship on a single tube (Fig. 2, not shown). In a further arrangement representations of each rail are simultaneously displayed on each one of a pair of tubes in an alternating sequence such that the display on each tube bridges the erase interval of the other tube (Fig. 3, not shown), control circuitry for such scanning being described with reference to block diagrams, Figs. 4 and 5 (not shown). A second pair of display tubes providing an expanded display of railjoint and bolt-hole regions may be employed and by pairing each of the latter with a tube displaying a standard pattern of such a region which is free from faults the corresponding displays may be compared in terms of equivalent video signals derived via respective television cameras to produce on departure from similarity an indication on an ordinary cathode-ray display tube (Fig. 6, not shown).